One of leading social media site Twitter reported that their sever is compromised by hackers and hackers may have gained access to information on 250,000 of its more than 200 million active users.

Anonymous hackers were able to gain access to around 250,000 accounts on the social networking site, including usernames, email addresses and passwords. According to some hackers, Chinese Anonymous hackers are involved but this was not confirmed by Chinese government. The Chinese foreign ministry could not be reached for comment Saturday, but the Chinese government has said those accusations are baseless and that China itself is a victim of cyber attacks.

Twitter discovered that the attackers may have stolen user names, email addresses and encrypted passwords belonging to 250,000 users they describe as "a very small percentage of our users." The company reset the pilfered passwords and sent emails advising the affected users.

Bob Lord, Twitter's director of information security, said the attack was "not the work of amateurs" and the company did not believe it was an isolated incident.

"Our investigation has thus far indicated that the attackers may have had access to limited user information – usernames, email addresses, session tokens and encrypted/salted versions of passwords – for approximately 250,000 users," Lord said. "As a precautionary security measure, we have reset passwords and revoked session tokens for these accounts.

"This attack was not the work of amateurs, and we do not believe it was an isolated incident. The attackers were extremely sophisticated, and we believe other companies and organizations have also been recently similarly attacked."